A lot of debate
has been had on just how much velocity is needed to obtain reliable
projectile expansion. So I put some projectiles to the test to find out.

For the information of readers, these projectiles were recovered from a
soft medium after being shot over a distance of 1000 yards.

The projectile on the left
is an unfired bullet to show the before and after effect.

The two well mushroomed projectiles on the left were fired out of my .338
RUM and had a
calculated impact velocity of only 1620 fps ave, at impact at the 1000
yards target.

The next two were fired using a full load out of my .338WM and had a calculated impact
velocity of 1373 fps ave. As you can see there is a big difference in expansion between
the 1620 fps and 1373 fps results.
The next two on the right, were fired using a reduced load out of my .338WM and had a
calculated impact velocity at 1000 yards of just 1228 fps ave. At this impact speed hardly
any expansiontakes place
So it just goes to show you that reliable bullet expansion can be obtained at a velocity
much lower than what most people think. The two projectiles on the left produced excellent
expansion at a relatively slow velocity of 1620 fps. Form these results it would appear that an
impact speed of about 1500 fps would give acceptable results with this particular projectile.
Hornady does not give a minimum expansion velocity on there bullets, but the similar
Accubond bullet is given a minimum expansion velocity of 1800 fps. So from these results, that
number is about right, with a reasonable safety margin for error as well.

For other bullets and different calibres it would be wise to test the minimum impact velocity
required for reliable expansion. Before using them for long range hunting.

All these bullets are 225 grain, premium Hornady Interbond projectiles in .338 calibre as
shown by the unfired bullet on the left. There are two samples of each impact velocity.